German submarine UD-4



Design and description

The O 21-class submarines were slightly smaller versions of the preceding since they lacked that class's minelaying capability. The boats had a length of overall, a beam of and a draught of. They displaced on the surface and submerged. The submarines had a crew of 60 officers and enlisted men.
For surface running, the boats were powered by two Sulzer diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the boats had a range of at and at 9 knots submerged. The submarines had a diving depth of.
The O 21 class was armed with eight torpedo tubes. Four of these were in the bow and two tubes were in the stern. The other pair were on an external rotating mount amidships. A reload was provided for each internal torpedo tube. UD-4 equipped with two [2 cm Flak 30, Flak 38 and Flakvierling 38|] Flak 38 AA guns.

Construction and career

The submarine was ordered on 8 July 1938 and laid down on 20 April 1939 as K XXVI at the shipyard of Rotterdamsche Droogdok Maatschappij in Rotterdam. During construction she was renamed O 26. Following the German invasion of 10 May 1940, the incomplete O 26 was captured at the yard by the invading forces. The Kriegsmarine decided to complete her and the launch took place on 23 November. She served in the Kriegsmarine as UD-4 and was commissioned on 28 January 1941, with Korvettenkapitän Helmut Brümmer-Patzig in command.
From January to April 1941, UD-4 served as school boat in Kiel when attached to the 1st Flotilla. In May, she was transferred to the 3rd Flotilla also in Kiel where she was used as a trial boat. She remained there until July that year. In August 1941, the boat was transferred to the 5th Flotilla also in Kiel where she was used as a school boat until December 1942. In January 1943, UD-4 was transferred to Gotenhafen where she served as a school boat for 24th Flotilla and 27th Flotilla until January 1945. From January to March 1945, she was based in Hela and transferred to the 18th Flotilla where she served as a school boat.
On 19 March 1945, UD-4 was decommissioned; she was scuttled in Kiel on 3 May.